Remarkable Peaks Research Articles

The hierarchical three-dimensional cobalt superstructure: Controllable synthesis, electromagnetic properties and microwave absorption

A close-packed hexagonal (HCP)-cobalt superstructure was synthesized on a large scale through a simple, yet low-cost liquid reduction method. The cobalt superstructure was assembled by nanoflakes with strong shape anisotropy. The permittivity (εr=ε′-jε″) and permeability (μr=μ′-jμ″) of cobalt superstructure were also studied as a function of frequency in microwave range of 1–18GHz. It is demonstrated that permittivity displays remarkable multiple dielectric resonance peaks. Multiple magnetic resonances were also exhibited for permeability, which were discussed based on the LLG equation and exchange resonance mode. Multiple dielectric and magnetic resonances were beneficial to widen microwave absorption bandwidth. The calculated reflection loss (RL) indicated that the cobalt superstructure had potential application as a promising candidate for microwave absorption. The reflection loss was attributed to two main reasons, one is the destructive interference, which was related to the thickness of the absorbent layer, and the other one was multiple microwave reflection due to the structure assembled by nanoflakes.

Dielectric property of MoS(2) crystal in terahertz and visible regions.

Two-dimensional materials such as MoS2 have attracted much attention in recent years due to their fascinating optoelectronic properties. The dielectric response of MoS2 crystal in both the terahertz (THz) and visible regions is studied in this work. Time-domain THz spectroscopy is employed for the THz property investigation. The real and imaginary parts of the complex dielectric constant of MoS2 crystal are found to follow a Drude model, which is due to the intrinsic carrier absorption. In the visible region, ellipsometry is used to investigate the dielectric response. The general trend of the complex dielectric constant is found to be described with a Lorentz model, while two remarkable dielectric response peaks are observed to be located at 1.85 and 2.03eV, which has been attributed to the splitting arising from the combined effect of interlayer coupling and spin-orbit coupling. This work can be the research foundation for future optoelectronic applications with MoS2.

Resonance magnetoelectric effect in an asymmetric magnetostrictive/piezoelectric trilayered composite structure

Resonant magnetoelectric(ME) effect in FeNi–PZT–FeCuNiSiB trilayered composite with asymmetric magnetostrictive layers is investigated. The magnetic layers facilitate effective excitation of bending oscillations in the structure due to the flexural deformation caused by the asymmetric stress distribution in the FeNi–PZT–FeCuNiSiB composite. As a result, two remarkable resonance peaks appear at bending resonance frequency f1 = 38.8 kHz and longitudinal resonance frequency f2 = 163.2 kHz, respectively. The magnetic field frequency dependence of ME voltage coefficient of the FeNi–PZT–FeCuNiSiB trilayer is distinct from those of FeNi–PZT–FeNi and FeCuNiSiB–PZT–FeCuNiSiB trilayers. Furthermore, the dual-peak ME effects at bending and longitudinal resonance frequencies are observed. The ME voltage coefficient at bending resonance is 1.18 V/Oe (14.75 V/cm Oe) that is 1.68 times larger than the value measured for a FeNi–PZT bilayer of similar dimensions. These results provide the possibility of implementing FeNi–PZT–FeCuNiSiB trilayered composite in magnetic-sensing devices.

The effects of different polymerization agents on structural and optical properties of (K0.5Na0.5)NbO3 nanopowders synthesized by a facile green route

( K 0.5 N 0.5) NbO 3 lead-free nanopowders were synthesized by a modified sol–gel method in different media: gelatin, starch and chitosan, as polymerization and stabilizer agents. The proper temperature needed for calcinating the prepared gel was obtained using thermogravometric analysis (TGA). Structural and optical properties of the prepared powders were investigated and compared using X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-Vis diffused reflectance spectroscopy. The XRD patterns of the synthesized samples confirmed the formation of the orthorhombic structure at 600°C calcination temperature with no remarkable extra peaks. TEM images showed that the morphologies of the particles prepared in the three different media are cubic with the average size of about 69, 34 and 49 nm for gelatin, starch and chitosan, respectively. The value of the energy band gap of the samples was calculated by diffused reflectance spectroscopy, using Kubelka–Munk method. Our results showed that the type of the polymerization agent is important in preparing KNN nanoparticles and affects the structural and optical properties of the synthesized samples.

Mesoscale eddy effects on the subduction of North Pacific mode waters

AbstractMesoscale eddy effects on the subduction of North Pacific mode waters are investigated by comparing observations and ocean general circulation models where eddies are either parameterized or resolved. The eddy‐resolving models produce results closer to observations than the noneddy‐resolving model. There are large discrepancies in subduction patterns between eddy‐resolving and noneddy‐resolving models. In the noneddy‐resolving model, subduction on a given isopycnal is limited to the cross point between the mixed layer depth (MLD) front and the outcrop line whereas in eddy‐resolving models and observations, subduction takes place in a broader, zonally elongated band within the deep mixed layer region. Mesoscale eddies significantly enhance the total subduction rate, helping create remarkable peaks in the volume histogram that correspond to North Pacific subtropical mode water (STMW) and central mode water (CMW). Eddy‐enhanced subduction preferentially occurs south of the winter mean outcrop. With an anticyclonic eddy to the west and a cyclonic eddy to the east, the outcrop line meanders south, and the thermocline/MLD shoals eastward. As eddies propagate westward, the MLD shoals, shielding the water of low potential vorticity from the atmosphere. The southward eddy flow then carries the subducted water mass into the thermocline. The eddy subduction processes revealed here have important implications for designing field observations and improving models.

Determination of ecological status and ecological preferences of phytoplankton using multivariate approach in a Mediterranean reservoir

The European Union Water Framework Directive includes phytoplankton as one of the mandatory five biological indicators to be used to assess the ecological status of surface waters. The objective of the study was determination of ecological status and ecological preferences of phytoplankton from April 2012 to June 2013, using multivariate approach in Alleben Reservoir in the southeast Turkey. The reservoir showed a warm monomictic stratification pattern (stratification in April–October 2012 vs. mixing in November 2012–March 2013). The reservoir was meso-eutrophic according to phosphorus, chlorophyll a, and transparence values. Phytoplankton biovolume reached remarkable peaks in autumn and spring. Phytoplankton species belong to functional groups of A, D, E, J, LO, LM, MP, P, and Y as descriptor. Phytoplankton trophic index (PTI) and assemblage index (Q) indicated the overall medium ecological status of Alleben Reservoir. PTI and Q indices may be appropriate phytoplankton metrics to assess the ecological status of the reservoir. Changes in environmental gradients significantly influenced the ecological preferences of species and phytoplankton abundance in the reservoir. Canonical correspondence analysis (CCA) confirmed that phytoplankton species were sensitive to environmental variability, with the first two axes of CCA able to explain 92.8% of the total variation and 37.1% of the cumulative percentage variance in the phytoplankton assemblage structure. Most effective explanatory factors (e.g., salinity, conductivity, pH, and temperature) played significant role (P = 0.002) in the seasonality of species.

Chemical speciation in concentrated aqueous solutions of CuCl2 using thin-film UV–visible spectroscopy combined with DFT calculations

In this work, a thin-film UV–visible spectroscopic technique has been developed and combined with time-dependent density functional theory (TD-DFT) calculations for the study of the chemical speciation in concentrated aqueous solutions of Cu(II)+Cl−. When the CuCl2 concentration changed from 0.05mol·kg−1 to 5mol·kg−1, the UV peak shifted from ~250nm to ~262nm. Similar shifts were recorded for CuCl2 solutions containing up to 5mol·kg−1 NaCl. Combination of the spectral data with our previous TD-DFT calculations provided a consistent model of the chemical speciation in the Cu(II)/Cl− system up to high concentrations of both components. The results obtained indicate that many of the previous conclusions regarding these solutions, drawn from a variety of techniques are unreliable. Under the present conditions, the only species detected were innersphere complexes with one or two Cl− ions bound to the aquated Cu(II) ion. For all the solutions, no remarkable peaks at ~280nm or 380nm, indicative of CuCl3− (aq) and CuCl42− (aq) respectively, were observed.

Assessing the Role of Water on the Electronic Structure and Vibrational Spectra of Monohydrated l-Aspartic Acid Crystals

In this work, we compare the calculated electronic and vibrational properties (infrared and Raman spectra) of anhydrous and monohydrated l-aspartic acid crystals to unveil the role of water in the later. This is accomplished through density functional theory (DFT) simulations within the Tkatchenko and Scheffler dispersion corrected generalized gradient approximation (GGA+TS). Both crystals are shown to have indirect band gaps and the simulations predict that water has a small effect on the Kohn–Sham band gap value (60 meV). Δ-sol corrected gaps, in contrast, exhibited a larger difference between the anhydrous and monohydrated crystals (main gap 0.30 eV larger for the latter). The conduction bands of the monohydrated species are much flatter because of structural changes produced by the presence of water, which leads to very large electron effective masses. However, the hole effective mass along the stacking direction of water molecules in the GGA+TS optimized monohydrated crystal is smaller than in other directions, suggesting that water stacking can improve on hole transport in similar bioorganic systems. These effects highlight the complex role of water on the carrier transport properties in monohydrated l-aspartic acid crystals, which is in contrast with the general belief that water simply increases the electrical conductance in molecular crystals. Finally, the calculated infrared and Raman spectra of the monohydrated phase exhibit molecular water vibrational signatures as well as water related peak shifts of as much as 100 cm–1 in comparison to those of the anhydrous structure. Remarkable water related Raman intensity peaks were obtained for the monohydrated crystal in the wavenumber ranges between 600 and 1000 cm–1 and between 2350 and 3450 cm–1, while for the infrared spectrum, a set of water absorption bands can be clearly identified in the 1550–1750 and 2800–3400 cm–1 wavenumber intervals.

Differential immune response of mallard duck peripheral blood mononuclear cells to two highly pathogenic avian influenza H5N1 viruses with distinct pathogenicity in mallard ducks

CK10 and GS10 are two H5N1 highly pathogenic influenza viruses of similar genetic background but differ in their pathogenicity in mallard ducks. CK10 is highly pathogenic whereas GS10 is low pathogenic. In this study, strong inflammatory response in terms of the expression level of several cytokines was observed in mallard duck peripheral blood mononuclear cells (PBMC) infected with CK10 while mild response was triggered in those by GS10 infection. Two remarkable and intense peaks of immune response were induced by CK10 infection within 24 hours (at 8 and 24 hours post infection, respectively) without reducing the virus replication. Our observations indicated that sustained and intense innate immune responses may be central to the high pathogenicity caused by CK10 in ducks.

Syntheses, crystal structures and fluorescent properties of two d 10-metal coordination polymers based on 1,5-naphthalenedisulfonic acid

The first examples of two d 10 metal coordination polymers based on 1,5-naphthalenedisulfonic acid and benzimidazole, namely, [Cd(bim)4(1,5-nds)] 1 and [Ag(bim)2]·½1,5-nds 2 (bim = benzimidazole, 1,5-nds = 1,5-naphthalenedisulfonic acid) were synthesized successfully under solvothermal conditions. Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR, TG-DSC, PXRD, UV–Vis, and DFT. 1 exhibits a 3D supramolecular structure which started from 1D helical chain. 2 also shows a 3D architecture which was assembled via π–π interactions and hydrogen bonds. The hydrogen bonds formed by 1,5-nds play an important role in increasing the dimensionality of architectures of 1 (from 1D to 3D) and 2 (from 0D to 1D). Moreover, both 1 and 2 show excellent luminescent properties, 335 nm for 1 (λ ex = 286 nm) and 341 nm and 389 nm for 2 (λ ex = 234 nm), and may be the suitable candidates of fluorescent materials. From UV–Vis spectra, the remarkable absorption peaks can be found at 276 nm for 1 and 271 nm for 2. The simulated UV–Vis spectra (290.30 nm for 1 and 271.64 nm for 2) by Gaussian 09 DFT correspond well with the experimental results. From the electron density distribution of frontier molecular orbitals, it is known that the two absorption bands are attributed to the intra-ligand electron transition from HOMO−26 to LUMO and from HOMO−3 to LUMO+1 for 1, from HOMO−1 to LUMO+18 and LUMO+19 for 2.

Structural Stability, Electronic and Optical Properties of Ni-Doped Boron Carbide by First Principles Calculation

The wide band gap, temperature stability, high resistivity, robustness of semiconducting boron carbide make it an attractive material for device applications.. Here the structural stability along with the electronic and the optical properties of Ni-doped boron carbides (B13C2) were studied using the first principle calculations based on plane wave pseudo-potential theory. The calculated results showed that Ni-doped in boron carbide was in preference to substituting C atom on the end of C-B-C chain, but it was difficult for Ni to substitute B atom in the center of the C-B-C chain or in the icosahedron. A representative stable structural unit containing Ni atom was [C-B-Nε+-[B11ε-, while the structural unit without Ni was [C-B-ε--[B12]ε+. The band structure, density of states (DOS) indicated that the coexistence of [C-B-Nε+-[B11ε-structural unit made electrical conductivity increased. Some new impurity energy levels appear in the band gap of Ni-doped B13C2, which can improve the conductivity of B13C2as well. Ni acts as an-type dopant. As the covalent bond of Ni-B was weaker than those of B-B and B-C, the thermal conductivity decreased for Ni-doped B13C2, thermoelectric property of Ni-doped boron carbides has been improved. The imaginary part of the dielectric function of Ni-doped B13C2has three remarkable peaks at 1.13, 3.89, and 6.05 eV. This reveals that doping with Ni can improve the photo-absorption efficiency of B13C2.

RESONANT MAGNETOELECTRIC EFFECTS IN Ni/Pb(Zr,Ti)O3/FeCo TRILAYERED SEMICIRCULAR COMPOSITES

Magnetoelectric (ME) effect has been studied in semicircular composites with a negative magnetostrictive/piezoelectric/positive magnetostrictive Ni/Pb(Zr,Ti)O3/FeCo trilayered structure. The ME behavior of the Ni/Pb(Zr,Ti)O3/FeCo is different from those in previous studies and zero-bias ME effects and four remarkable resonant peaks have been observed in the dependence of the ME voltage coefficient on the magnetic field frequency in the 1–150 kHz range. The effective excitation of the acoustical oscillations provided by the positive and negative magnetostrictive layers is responsible for the multifrequency ME effects. The results open up a suitable way to make multifunctional devices with multi-resonant-frequencies and/or zero-bias operations.

Observing Far-Distance Ionosphere Disturbance Effect

Using HF-Doppler detector we have been observed ionosphere disturbance continuously for about 20 years. Firstly, We gave a theoretic explanation to normal frequency-shift records, then using two typical cases we pointed out that in china there exist F2 layer infrasonic disturbance which due to severe weather. Through analyzing their spectrums, we found three remarkable peaks. And comparing with foreign researchers, we indicated that infrasonic disturbances possess local features. Finally, we concluded local features of infrasonic disturbances occurring in our area.

Bacterial colonization of the freshwater planktonic diatom Fragilaria crotonensis

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 66:87-94 (2012) - DOI: https://doi.org/10.3354/ame01560 Bacterial colonization of the freshwater planktonic diatom Fragilaria crotonensis Petr Znachor*, Karel Šimek, Jiří Nedoma Biology Centre of Czech Academy of Sciences, v.v.i., Institute of Hydrobiology, Na Sádkách 7, České Budějovice 37005, Czech Republic *Email: znachy@hbu.cas.cz ABSTRACT: In 2006, the seasonal course of bacterial colonization and silification rates of a colonial diatom Fragilaria crotonensis were studied at 2 distinct depths (‘surface’ 0.5 m and Zeu, the depth of 1% remaining surface photosynthetically active radiation) in the eutrophic Římov Reservoir (Czech Republic). In the study period (July to September), Fragilaria dominated the phytoplankton and formed remarkable subsurface peaks of biomass at Zeu. Diatoms living under light-limited conditions at Zeu displayed lower silification rates measured with the fluorescence probe 2-(4-pyridyl)-5-{[4-(2-dimethylaminoethyl-aminocarbamoyl)methoxy]phenyl} oxazole (PDMPO) and were significantly more colonized by bacteria than at the surface (seasonal means 7.8 and 5.0 bacteria per Fragilaria cell, respectively). In 3 additional experiments using double-stained Fragilaria cells (PDMPO and 4’,6-diamidino-2-phenylindole [DAPI]), diatom cells with no PDMPO fluorescence were significantly more colonized by bacteria regardless of the depth, indicating that bacterial colonization reflects the physiological state of the diatoms. As an apparent consequence of a flood event in August, the Fragilaria assemblage was composed of 2 temporally isolated sub-populations differing markedly in the cell length, cell surface area and extent of bacterial colonization. Although both Fragilaria sub-populations showed similar silification rates, the late summer (post-flood) Fragilaria sub-population with smaller cells showed a significantly lower bacterial colonization, while the difference in bacterial colonization between the depths remained consistently significant throughout the study. Our results imply that bacterial colonization of diatom cell surfaces is modulated by both diatom growth and changes in population structure over the season. KEY WORDS: Fragilaria crotonensis · Diatoms · Bacterial colonization · Physiological state · Silification · PDMPO Full text in pdf format PreviousNextCite this article as: Znachor P, Šimek K, Nedoma J (2012) Bacterial colonization of the freshwater planktonic diatom Fragilaria crotonensis. Aquat Microb Ecol 66:87-94. https://doi.org/10.3354/ame01560 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 66, No. 1. Online publication date: April 04, 2012 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2012 Inter-Research.

Effect of porcelain shape for strain behavior of strengthened porcelain in impact test

Four types of strengthened porcelains were evaluated by an impact examination machine based on ASTM C368-88. The waveform of strain developed on impact was measured by a strain gauge pasted on the inside surface and the outside surface, vertical and horizontal direction of porcelain. In minute scales, procelain deformed into an oval shape as a whole by an impact onto the rim, where the higher tensile strain occurred in the horizontal direction on the inside surface of porcelain. The maximum tensile strain occurred at the impact point. The waveform of strain, that showed two remarkable peaks, was greatly affected by porcelain shape. In addition it was more or less affected by measurement conditions such as impact energy, weight or speed of hammer, weight for holding, and position of backstops.

Superhorizon fluctuations and acoustic oscillations in relativistic heavy ion collisions

We focus on the initial state spatial anisotropies, originating at the thermalization stage, for central collisions in relativistic heavy-ion collisions. We argue that the physics of fluctuations at the early stages of heavy ion collisions has strong similarities with the physics of density fluctuations in the early universe which give rise to remarkable acoustic peaks in the cosmic microwave background radiation (CMBR) power spectrum. Following the method of analysis in CMBR physics, we propose that a plot of root mean square values of the flow coefficients $\sqrt {\overline {v_n^2 } } \equiv v_n^{rms} $ , calculated in a laboratory fixed coordinate system, for a large range of n from 1 to about 30, can give non-trivial information about the initial stages of the system and its evolution. We also argue that for all wavelengths λ of the anisotropy (at the surface of the plasma region) much larger than the acoustic horizon size $H_s^{f^r } $ at the freezeout stage, the resulting values of V should be suppressed by a factor of order $2H_s^{f^r } /\lambda $ .

Structural stability, electronic and optical properties of Ni-doped 3C–SiC by first principles calculation

Structural stability along with the electronic and the optical properties of intrinsic 3C–SiC and Ni-doped 3C–SiC were studied by the first principles calculation. For the Ni-doped 3C–SiC, substitution of Ni in Si sub-lattice is energetically more favorable than that in C sub-lattice. Some new impurity energy levels appear in the band gap of Ni-doped 3C–SiC, which can improve the conductivity of 3C–SiC. The imaginary part of the dielectric function of Ni-doped 3C–SiC has three remarkable peaks at 0.69 eV, 2.35 eV, and 4.16 eV. This reveals that doping with Ni can improve the photo-absorption efficiency of 3C–SiC. In the absorption spectrum of Ni-doped 3C–SiC, the absorption edge red-shifts towards the far-infrared region. Furthermore, three new absorbing peaks emerge in the near-infrared region, visible region, and middle-ultraviolet region. These features confer Ni-doped 3C–SiC qualifications of a promising optical material.

Spectroscopic studies on aquatic angiosperm

Reflectance, transmittance and absorbance spectra were observed of Hydrobryum japonicum, a kind of Aquatic angiosperm, over the wavelength range from 300 to 780 nm. Three remarkable peaks were observed at 380, 430, and at 680 nm in the absorbance curve, which were assigned to the two pigments flavonoid and chlorophyll. The functions of these pigments of making photosynthesis inevitable for the botanical activity and of protecting the plant from the heat given by the sunlight were discussed.

E-1-1 体内埋込型人工心臓のEMC : 生体から導線が伸びている場合の生体への電磁的影響の検討(E-1 生体治療・計測,口頭発表:生体治療・医療,バイオ操作・検査)

This paper addresses EMC of an implantable artificial heart connected by a conducting wire (drive line) and influence of the emitted electromagnetic noise on the human body. Conducting wire length and human height may cause electrical resonance. At such times, the current through the conducting wire and the human body could increase conspicuously. We determined the current passing through the human body attached the conducting wire by both FDTD electromagnetic simulation and experimental observation. A cylinder model was used to imitate the human trunk. It was placed at the center of a shield room and subjected to electromagnetic plane waves with wavelengths ranginge from 80 MHz to 1 GHz. Experimental results show that the current through the human body was generally in the range of 0.25-2.3 mA (100-400MHz) with three remarkable current peaks. Simulation results show higher average current and lower peak frequency compared to the experimental results.

Study on resonance magnetoelectric effect of layeredNi/Pb(Zr,Ti)O3/TbFe2 composites

Layered magnetoelectric Ni/PZT/TbFe2 composites have been prepared by electroless deposition and bonding method. The influence of the Ni layer thickness on ME coupling and resonance frequency is discussed. The results show that the magnetoelectric coefficient of Ni/PZT/TbFe2 composites changes differently from that of other composites and two remarkable resonance peaks have been observed. The magnetoelectric voltage coefficient at the first-order longitudinal resonance mode increases as the Ni layer thickness increases. Both experimental and calculated data reveal that the first-order bending resonance frequency fr1 and longitudinal resonance frequency fr2 increase with the Ni layer thickness.